Commitments and Contingencies	6 Months Ended
Jun. 30, 2026
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies License Agreements In September 2014, the Company entered into the UCLB License Agreement. In connection with the UCLB License Agreement, the Company is required to make annual license payments and may be required to make payments to UCLB upon the achievement of specified milestones, including upon regulatory approval for obe-cel. During the six months ended June 30, 2026, the Company paid or accrued amounts relating to the income allocable to the value of the sublicensed intellectual property rights and royalties. On July 18, 2025, the Company was notified by the European Commission that the Company has been granted marketing approval for AUCATZYL (obecabtagene autoleucel) for the treatment of adult patients (26 years and older) with r/r B-ALL which triggered a £6.0 million regulatory milestone payment that was paid by the Company in accordance with the UCLB License Agreement. Contractual obligations In previous periods, the Company has entered into agreements with certain advisory firms. The Company is obligated to make specified payments upon the achievement of certain strategic transactions involving the Company. There were no fees paid or payable to strategic advisory firms during the three and six months ended June 30, 2026 and 2025, respectively. The Company has estimated the probability of the Company achieving each potential milestone in relation to the agreements with UCLB and its agreements with certain advisory firms in accordance with ASC 450. The Company considers regulatory approval, commercial milestones and execution of collaboration agreements probable when actually achieved. Furthermore, the Company recognizes expenses for clinical milestones when their achievement is deemed probable. The Company concluded that as of June 30, 2026, there were no other milestones for which the likelihood of achievement was currently probable. Capital Commitments As of June 30, 2026, the Company’s unconditional purchase obligations for capital expenditures totaled $1.5 million and included signed orders for capital equipment and capital expenditures for construction and related expenditures relating to its properties in the United Kingdom and the United States. The Company expects to incur the full amount of these obligations within one year. Master Supply Commitments As of June 30, 2026, the Company’s unconditional purchase obligations with Miltenyi Biotec GmbH for reagents and consumables totaled $1.9 million, which the Company expects to incur within one year. On January 21, 2026, the Company, entered into a Master Service Agreement with AGC Biologics S.p.A (“AGC”) for the manufacture and supply of lentiviral vector (the “AGC Agreement”), a raw material which is used in Company’s manufacture of CAR-T products for clinical and commercial use. The AGC Agreement replaces and supersedes the prior arrangement between the Company and AGC, pursuant to which AGC has provided similar products and services. The Agreement sets forth the general terms and conditions applicable to AGC’s provision of products and services to the Company; specific projects will be set forth in individual work orders executed separately by the parties. The AGC Agreement contains customary provisions regarding order placement and fulfillment, governance, regulatory support, change management, risk allocation, intellectual property, and confidentiality. The AGC Agreement runs for a fixed term of ten years, and may be terminated by either party for default, or by the Company upon written notice (subject, in the latter case, to the payment of certain fees by the Company). The AGC Agreement is non-exclusive with respect to each party. However, under the Agreement and the initial statement of work thereunder, the Company has committed to purchase a minimum of 14 batches of lentiviral vector during the first two calendar years of the term, and to purchase a minimum value of EUR 25 million of products and services during the subsequent five-year period. The AGC Agreement also provides AGC with the first right to negotiate with the Company regarding the provision of new manufacturing activities in relation to obe-cel. BioNTech License and Option Agreement - Product Options gain contingency As the Product Options within the BioNTech License and Option Agreement were an embedded feature within a freestanding financial instrument, the Company assessed if the Product Options should be accounted for as a derivative under ASC 815. However, the Company determined the Product Options met the scope exception for derivative accounting under ASC 815 and therefore should be accounted for a gain contingency under the scope of ASC 450. As of June 30, 2026 and December 31, 2025, the Product Options were not exercised and, therefore, no amounts were recognized. Refer to Note 15, “Liabilities related to future royalties and milestones, net” for further details about the BioNTech Agreements. Legal Proceedings From time to time, the Company may be a party to litigation or subject to claims incident to the ordinary course of business. Regardless of the outcome, litigation can have an adverse impact on the Company due to defense and settlement costs, diversion of management resources and other factors. The Company was not a party to any litigation and did not have contingency reserves established for any liabilities as of June 30, 2026 and December 31, 2025. Indemnification Agreements In the normal course of business, the Company enters into contracts and agreements that contain a variety of representations and warranties and provide for general indemnification. The Company’s exposure under these agreements is unknown because they involve claims that may be made against the Company in the future. To date, the Company has not paid any claims or been required to defend any action related to its indemnification obligations. However, the Company may record charges in the future as a result of these indemnification obligations. In accordance with the indemnification agreements entered into with relevant individuals in accordance with the Company’s Articles of Association, the Company has indemnification obligations to its directors, officers and members of senior management for certain events or occurrences, subject to certain limits, while they are serving at the Company’s request in such capacity. There have been no claims to date under these indemnification agreements, and the Company has director and officer insurance that may enable it to recover a portion of any amounts paid for future potential claims. SME Research and Development (R&D) tax credit In the accounting period to December 2023, based on the relevant tax legislation, the Company met the conditions of the research and development (“R&D”) intensive scheme, and therefore submitted its corporate tax return on this basis. This is subject to agreement by the United Kingdom tax authority. The tax authority’s non-statutory guidance includes some expenditure in the calculation of whether a company meets the R&D intensive scheme, which is in conflict with the criteria in the tax legislation. The position is uncertain and the legislation is currently untested in the United Kingdom courts. The Company is engaged in ongoing discussions with the United Kingdom tax authority regarding the R&D tax credit claimed by the Company in its corporate tax return for the accounting period to December 2023. If the Company’s claim under the R&D intensive scheme is unsuccessful, there will be a material reduction in the value of the tax credit obtained (18.6% as opposed to 26.97% net benefit), and certain amounts claimed by the Company may be disallowed. However, in that instance, the Company expects that normal U.K. small and medium enterprise (“SME”) relief will be available. The Company recorded a SME research and development tax credit receivable of $19.0 million (translated from pounds sterling into U.S dollars at the exchange rate in effect on March 31, 2026) within prepaid expenses and other current assets utilizing the net benefit of 18.6%. During the three months ended June 30, 2026, the Company received a partial payment of its SME R&D tax credit relating to the accounting period ended December 2023 of $19.0 million (translated to U.S. dollars on the date of receipt). Should the uncertainty over the remaining payment be resolved in the Company’s favor, this would result in a gain and would be accounted for as a gain contingency under the scope of ASC 450. This uncertainty only applies to one accounting period.

In September 2014, the Company entered into the UCLB License Agreement. In connection with the UCLB License Agreement, the Company is required to make annual license payments and may be required to make payments to UCLB upon the achievement of specified milestones, including upon regulatory approval for obe-cel. During the six months ended June 30, 2026, the Company paid or accrued amounts relating to the income allocable to the value of the sublicensed intellectual property rights and royalties.

The Company has estimated the probability of the Company achieving each potential milestone in relation to the agreements with UCLB and its agreements with certain advisory firms in accordance with ASC 450. The Company considers regulatory approval, commercial milestones and execution of collaboration agreements probable when actually achieved. Furthermore, the Company recognizes expenses for clinical milestones when their achievement is deemed probable. The Company concluded that as of June 30, 2026, there were no other milestones for which the likelihood of achievement was currently probable.

On January 21, 2026, the Company, entered into a Master Service Agreement with AGC Biologics S.p.A (“AGC”) for the manufacture and supply of lentiviral vector (the “AGC Agreement”), a raw material which is used in Company’s manufacture of CAR-T products for clinical and commercial use. The AGC Agreement replaces and supersedes the prior arrangement between the Company and AGC, pursuant to which AGC has provided similar products and services.

The Agreement sets forth the general terms and conditions applicable to AGC’s provision of products and services to the Company; specific projects will be set forth in individual work orders executed separately by the parties. The AGC Agreement contains customary provisions regarding order placement and fulfillment, governance, regulatory support, change management, risk allocation, intellectual property, and confidentiality. The AGC Agreement runs for a fixed term of ten years, and may be terminated by either party for default, or by the Company upon written notice (subject, in the latter case, to the payment of certain fees by the Company). The AGC Agreement is non-exclusive with respect to each party. However, under the Agreement and the initial statement of work thereunder, the Company has committed to purchase a minimum of 14 batches of lentiviral vector during the first two calendar years of the term, and to purchase a minimum value of EUR 25 million of products and services during the subsequent five-year period. The AGC Agreement also provides AGC with the first right to negotiate with the Company regarding the provision of new manufacturing activities in relation to obe-cel.

As the Product Options within the BioNTech License and Option Agreement were an embedded feature within a freestanding financial instrument, the Company assessed if the Product Options should be accounted for as a derivative under ASC 815. However, the Company determined the Product Options met the scope exception for derivative accounting under ASC 815 and therefore should be accounted for a gain contingency under the scope of ASC 450. As of June 30, 2026 and December 31, 2025, the Product Options were not exercised and, therefore, no amounts were recognized. Refer to Note 15, “Liabilities related to future royalties and milestones, net” for further details about the BioNTech Agreements.

From time to time, the Company may be a party to litigation or subject to claims incident to the ordinary course of business. Regardless of the outcome, litigation can have an adverse impact on the Company due to defense and settlement costs, diversion of management resources and other factors. The Company was not a party to any litigation and did not have contingency reserves established for any liabilities as of June 30, 2026 and December 31, 2025.

In the normal course of business, the Company enters into contracts and agreements that contain a variety of representations and warranties and provide for general indemnification. The Company’s exposure under these agreements is unknown because they involve claims that may be made against the Company in the future. To date, the Company has not paid any claims or been required to defend any action related to its indemnification obligations. However, the Company may record charges in the future as a result of these indemnification obligations.

In accordance with the indemnification agreements entered into with relevant individuals in accordance with the Company’s Articles of Association, the Company has indemnification obligations to its directors, officers and members of senior management for certain events or occurrences, subject to certain limits, while they are serving at the Company’s request in such capacity. There have been no claims to date under these indemnification agreements, and the Company has director and officer insurance that may enable it to recover a portion of any amounts paid for future potential claims.

In the accounting period to December 2023, based on the relevant tax legislation, the Company met the conditions of the research and development (“R&D”) intensive scheme, and therefore submitted its corporate tax return on this basis. This is subject to agreement by the United Kingdom tax authority. The tax authority’s non-statutory guidance includes some expenditure in the calculation of whether a company meets the R&D intensive scheme, which is in conflict with the criteria in the tax legislation. The position is uncertain and the legislation is currently untested in the United Kingdom courts. The Company is engaged in ongoing discussions with the United Kingdom tax authority regarding the R&D tax credit claimed by the Company in its corporate tax return for the accounting period to December 2023. If the Company’s claim under the R&D intensive scheme is unsuccessful, there will be a material reduction in the value of the tax credit obtained (18.6% as opposed to 26.97% net benefit), and certain amounts claimed by the Company may be disallowed. However, in that instance, the Company expects that normal U.K. small and medium enterprise (“SME”) relief will be available. The Company recorded a SME research and development tax credit receivable of $19.0 million (translated from pounds sterling into U.S dollars at the exchange rate in effect on March 31, 2026) within prepaid expenses and other current assets utilizing the net benefit of 18.6%. During the three months ended June 30, 2026, the Company received a partial payment of its SME R&D tax credit relating to the accounting period ended December 2023 of $19.0 million (translated to U.S. dollars on the date of receipt). Should the uncertainty over the remaining payment be resolved in the Company’s favor, this would result in a gain and would be accounted for as a gain contingency under the scope of ASC 450. This uncertainty only applies to one accounting period.